Process for solvent extraction of oils



Y Jan. 25, 1938.

U. B. BRAY PROCESS FOR SOLVENT EXTRACTIONl OF OILS Filed Feb. 19, 1954-I INVENTOR Zinc B Br'ay ATTORNEY.

Patented Jan. 25,` i938 @its Prem# ortica PROCESS FOR SOLEEIT EXTRACTION0F Unic' n. Bray, rains verses Estates, Calif., as-

slgnor to Union Oil Company of California, Los Angeles, Calif., acorporation of California Application February 19, 1934, semi No.111,963

Claims.

' by the use of solvents which selectively dissolve the undesirablehydrocarbons but which exhibit only a very limited solvent power uponthe desirable paraflinic hydrocarbons.

When I use the term paramnic hydrocarbons I mean those highly saturatedcompounds which are present in petroleum and are characterized bya lowtemperature viscosity susceptibility, i. e., they exhibit a minimum'change in viscosity for a. given change in temperature. They also arecharacterized by relative stability to air and sunlight, exhibitinglittle tendency toward discoloration or sludge formation. This denitionis not meant to include those compounds which are usuallysolid orsemi-solid at ordinary temperatures and which are known as "wax orpetrolatum; but, of course, it is obvious that my invention is meant toalso include the selective extraction of waxy oils. As a matter ofconvenience hereafter, I will refer to the undesirable components, suchas oleiinic, naphthenic and/or aromatic hydrocarbons, as thenon-parafnic components of petroleum. These fractions are characterizedby a relatively high temperature viscosity susceptibility and arerelatively un-l vstable to air and sunlight,` exhibiting discolorationand sludge formation` 'A number of selective solvents for extractionhave been found; for example, it has been shown that such materials asaniline, chloraniline, nitrobenzene, dichlorethyl ether, phenol,chlorophenol, cresol and cresol with a small proportion` of water, forinstance 4%, are highly selective as solvents for the non-paraiiinichydrocarbons. When these solvents are commingled with petroleum orpetroleum fractions under the proper conditions of temperature,the-undesirable nonparainic hydrocarbons passinto solution to a greateror less extent but a substantial propor'- of the container and forms anextract phase when relatively heavy"solvents are employed. The`relatively light paraiiinic hydrocarbons rise to the top of the vesseland form a ramnate phase.

These phases are then readily separable by ordinary decantation means.The rainate phase isv usually found to contain a smallquantity of theselective solvent and the extract phase ordinarily contains a relativelylarge quantity of the sola vent. These fractions may be puried bydistil- 5A lation whereby the solvent is distilled away from thehydrocarbon oils. A

In the usual solvent extraction of mineral oil with the above mentionedselective solvents, the separation is not complete. Particularly, all.of the parainic hydrocarbons, i. e. the more valuable lubricants, arenot obtained inthe raflinate phase but instead,some of the high gradeparafflnic oil fractions are found in the extract phase. Also, theextract phase may contain kcertain fractions of oil characterized byproperties intermeldiate low and high grade. lThese fractions arel notdesired in the nal rafllnate but are valuable as second grade oils whenseparated from. the fractions of low quality.

-It has been known in the solvent a 20 extraction art kthat after makinga primary separationof rafli- 'natefromjextract, additional fractionscan be made to separate from the extract phase by one or more'reductionsof temperature which correspondingly reduce the solubility of these oilsof relatively high parainicity in the extract phase. These oils `thenform intermediate -rainates which can be separately recovered bydecantation from the remaining extract phase. The solubility of oils ofrelatively high paralniclty in the extract phase can also be reduced bythe addition of an anti-solvent thereto, the presence of which causes aphase-separation between anintermediate raiiin'ate and remaining extractphase. This intermediate rainate 'comprises second grade oil ofquality'superior -to the oil remaining dissolved in the extract phase. V

An anti-solvent maybe Ydefined/.as a"`iate'rlalwhich tends to preventthe solution of a hydro- 40 carbon fraction which, except for thepresence of the anti-solvent, would be dissolved in the extract phaseupon extraction of the oilwith a selective solvent. A number vofsubstances are suitable for use as an anti-solvent; for instance liquidnormally gaseous hydrocarbons such as liquid ethane, propane or butane,or methyl, ethyl or isopropyl -alco ols, methyl cellosolve (monomethylether o! ethylene glycol) and other oxygenated compounds such as acetoneor methyl 50 acetate. Evenrwater Vmay-be used as an antisolvent .whenthe -selective solvent with which it is employed vis at least partlysoluble therein. AOne vor more of these anti-solvents may be employed.

vlu

Some cases, the addition of an anti-solvent lil to the extract phaserenders temperature reduction unnecessary to separate relatively highquality oil fractions therefrom. In other cases, refrigeration of theextract phase will be necessary but will be less than when noanti-solvent is present. In a solvent extraction process of thischaracter, the expense of refrigeration is la substantial item in thecost of operation. My process lowers this cost. y

Under certain conditions, the anti-solvent which may be' employed may bea substance which is a selective solvent when employed alone. Forinstance, there may be mixed with the extract phase to function as ananti-solvent a; selective solvent having less solvent power forthehigher grade material present therein than the solvent power ofthe'selective solvent originally used to produce the extract. As anexample, oil may be treated with chloraniline or a mixture of liquidsulphur dioxideand benzene to obtain an extract phase. These solventsare characterized by high solvent power for higher grade material. Tothe extract phase thus produced there may be added liquid sulphurdioxide or other solvent having relatively less solvent power for thehigher grade material. For this reason and under these conditons,certain selective solvents may be employed as anti-solvents and by theirpresence in the extract phase the higher grade fractions therein arerejected to form an intermediate railinate.

I have found that when the anti-solvent employed is a liquid, normallygaseous substance such as liquid propane, butane, sulphur dioxide or thelike, the rejection of desirable oils from the extract phase by thepresence 'of said antisolvent is aidedewhen the pressure is sutlicientlyreduced in the rejection stage to cause evaporation of a portion. of theanti-solvent, thereby reducing the temperature of the mixture of theextract phase and anti-solvent remaining liquid. In this case theliquid, normally gaseous material, for instance ethane, propane, butaneor similar substances, not'only functions as an antisolvent to removethe relatively high grade fractions from the extract phase but alsooperates as an internal refrigerant. After evaporation for internalrefrigeration, sufficient amounts of said liquid, normally gaseousmaterial should remain associated in the liquid phase with the extractto function as'an anti-solvent.

It is an object of my invention to separate anoil by means of aselective solvent into a raflinate phase and an extract'phase and tointermix saicl It is another object of my invention to recover anintermediate rafiinate from said extract by mixing the extract phasewith a liquid, normally gaseous anti-solvent and employing saidantisolvent as an internal refrigerant to aid in reducing thetemperature of the extract phase to prcmote the separation of theintermediate raflina e.

The refrigeration of the extract phase for rc- Jection of intermediateraiiinate can also be omitted or reduced in degreeby removing aconsiderable portion of the selective solvent from the extract phasebefore treating the extract phase with a`n anti-solvent at thetemperature appropriate for separation of the relatively paraflinicfractions. In addition to the effect of the antisolvent, the solubilityof the relatively valuable parainic fractions in the extract is reducedby the lpresence of a lower proportion of selective solvent. In somecases; unless the proportion of solvent in the extract phase is reduced,excessively large amounts of anti-solvent must be added to cause phaseseparation of the extract phase `and rejection vof an intermediaterafllnate.

Therefore, it is another object of my invention to separate an oil bymeans of a. selective solvent into a raffinate and an extract, remove aportion of the selective solvent from the extract phase and thenintermix said extract with an anti-solvent to separate an intermediateraftlnatefrom the extract phase.

The gure is a schematic arrangement of one form of apparatuswhich may beemployed to carry out my process.

Referring to the figure, oil enters the system via line I0 controlled byvalve II by action of pump I2 and passes into primary extractor I3,wherein it is countercurrently extracted with selective solventintroduced through line I4 controlled by valve I5 by action of pump I6.Raflinate phase from extractor I3 is removed via line I 1 and valve I8and passes through coil 2,0 in heater 2l prior to entrance intosecondary extractor 23 via line 23. Countercurrent extraction isagainaccomplished in 23 by selective solvent introduced through line 25controlled by valve 26 by action of pump 2l.

passes through coil 32 in heater 33 and line 34 connected with vaporseparator 35. Its temperature is raised suiciently in 32 to vaporize in35 the selective solvent associated therewith and these vapors areremoved through line 36 controlled by valve 31. High grade rainate exitsvia line 38 and valve 39. Intermediate extract phase is removed fromsecondary extractor 23 through line 40 controlled by valve 4I by actionof pump 42. 1

When the same solvent or a different solvent of substantially the sameor lower solvent power is employed in both extractors I3 and 23, theraflinate from the primary extractor is preferably heated beforeextraction in the secondary extractor in order to increase the amount ofintermediate extract produced yin the secondary extractor. When thesolvent employed in 23 has greater. solvent power than the solvent usedin I3, heater V2i may be omitted in some cases.

Extract phase from primary extractor I3 passes Rafiinate phase issuesfrom` extractor23 through 30 controlled by valve 3| and.

through line 45 controlled by valve 46. When it is desired to lower theproportion of selective solvent in theextract phase prior to theaddition of the anti-solvent thereto, valve 41 inline 45 may be entirelyclosed in order to by-pass the stream of extract phase via line 48 andvalve 49.

In this event, the extract phase. flows through amount of selectivesolvent therefrom in 55.

These vapors pass from the system via line 56,

controlled by valve 51. The extract phase containing the desiredproportion of selective sol-.

vent passes from vaporizer 55 through line 60 controlled by valve 6| byaction of pump 62. It then passes through coil 63 in heat exchangerelationship with coil 50. The material then iiows through line 64 andvalve 65. The temperature f the extract phase may be further lowered byv the desired proportion of solvent. In some cases it may not benecessary to lower theiproportion of solvent to oil in the extract phasepassing from extractor I3 via line 45 before the addition of theanti-solvena In that event valves 49 and 65 are closed and valve 41remains open.

Anti-solvent is introduced into the stream 0f extract owing through line45 by line 10 con.-

trolled by valve 1| by action of pump 12. The" combined vstream passesinto oriice mixer 13` Where thorough agitation occurs, after which itpassesinto cooler 15 via line 14. Cooling may be accomplished by anydesired means such as by external refrigeration but when liquid,normally gaseous anti-solvent is employed I prefer to employ internalrefrigeration. That is, the pressure is suiciently reduced in cooler 15to vaporize a portion oi the anti-solvent with consequent cooling of theremaining liquid. The vaporized portion of the -anti-solventexits fromcooler 15 through line 16 controlled by valve 11. The extract phase andanti-solvent are sufciently cooled in 15 to cause phase separation inseparator 80 to which the chilled mixture passes by -solvent and theselective solvent.

action of pump 8| through line 82 controlled by valve 83. Extract phasefrom. passes through line-84 controlled by valve 85, through heater 86and line 81 into vapor separator 88. The stream is suiciently heated in86 to vaporize theanti- These vapors pass through exit line 89controlled by valve 90. 'Ihe low grade extract oil is removed throughline 9| controlled by valve 92.

Rafnate phase rejected in separatorv 80 passes through line 93controlledby valve 94 through heater 95 and line 96 into vapor separator 91.Suicient heat is imparted in 95 to vaporize the anti-solvent and anyselective solvent associated with the intermediate grade rainate. Thesevavalve 99. In some cases it is desired to heat sufiiciently to removeonly the anti-solvent from the oil and solvent in vapor separator 91.Th'e intermediate grade raiiinate exits from 91 through line |00controlled by valve |0| by action of pump |02.

'Although theintermediate grade raffinate iowing through line V|00 andthe intermediate grade extract produced in secondary extractor 23 may beseparately recovered and separately distilled to obtain nal productswithin the desired boiling point range, I prefer to intermix thesestreams flowing through lines |00 and 40. This combined stream .isheated' in -heater |05 prior to passage into fractionating tower |06 vialine |01. Fractionating tower |06 may be provided with the usual traysI|08 and other usual appurtenances.

Vapors exit from fractionating tower |06 via line |09 controlled byvalve ||0. vResidual-oil passes from the tower through line controlledby valve ||2. Intermediate side cut distillates can be taken from tower|06 by lines ||3 and |4 controlled by valves ||5 and ||6 respectively.Fractionation in |06 may be accomplished under vacuum and/or with steaminjection as desired.

As an example of the operation of the apparatus disclosed in the gure, adewaxed Santa Fe Springs lubricating distillate characterized by' A. P.I. gravity at 60 F. of 19.8, carbon residue of 0.24%, acid numberof'0.16 and viscosity gravity constant. of 0.874 was extracted inextractor |3 with 175 volume percent. Ichloraniline at n45 F. Theraffinate thus produced was heated in.

, acid number of 0.04 and viscosity gravity constant Sucient extractphase passing from extractor I3 Wasbypassed via line 48 through heater52 and vapor separator 55'so that upon re-uniting with the streampassing through valve 41 the combined stream comprised 70 volumepercent.

chloraniline based on the original charge of oil. To this stream wasadded volume percent. liquid propane as an anti-solvent. Sufcientpropane was vaporized in cooler 15 to reduce the temperature of themixture to 40 F. at which phase separation occurred. Extract removed vialine 9| had an A. P. I. gravity at 60 F. ofv'1.3. Rejected intermediateranate freed of propane and chloraniline passing through line |00 had anA. P. I. gravity at 60 F. of 21.9 carbon residue of 0.16%, acid numberof 0.04 and viscosity gravity constant of 0.857; In one modifiedoperation, only the propane was vaporized from the intermediate rejectedrainate in 91 and the unvafporized residue in line |00 was combinedwiththe intermediate extract passing through line 90. The mixture was4distilled under vacuum into separate cuts of desired boiling point rangein heater |05 and fractionating tower |06.

As a further modification of my process, ex tractor 23 may be omitted insome cases, all ofthe extraction` taking place in I3. In -this event,heater 2| is employed to distill the selective solvent from 'theraflinate passing through line |1.-

It will be understood that the foregoing is merelyillustrative ofcertain embodiments of my invention and that many modifications may be.made therein without departing from the spirit of my invention. s

I claim:

fili4 1. A process for the separation of parafinic' and non-paralnicfractions from mineral oil containing thesame which'comprises extractingsaid oil with a selective solvent, separating the extract I phasesoluble in said solvent from the rainate phase insoluble therein,reducing the selective solvent'content of said extract phase, thencommingling said extract phase with an anti-solvent and separating fromsaid extract phase an intermediate raiiinate` rendered insoluble in saidextract phase by said anti-solvent said intermediate raffinatecontaining the bulk of said anti-solvent.

2. A process for the separation'of paraiinic and non-paraffinic'fractions from mineral oil containing thesame which comprises extractingsaid oil with a selective solvent, Aseparating vthe extract phasesoluble in said solvent from the raiiinate phase insoluble therein,reducing the selective solvent content of said extract phase,then

commingling said extract phase with an anti-solvent, cooling saidextract phase, and separating from said extract phase an intermediateraffinate n portion of said anti-solvent, cooling said extract .phase byinternal refrigeration and separating from said extract phase anintermediate raiiinate rendered insoluble in said extractphase by said`anti-solvent said intermediate raflinate containing the bulk of saidanti-solvent.

, 4. A process for the separation of paraiilnic and non-paraiiinicfractions from mineral oil containing the same which comprisesextracting said` oil with a selective solvent,v separating the extractphase soluble in saidisolvent from the rafnnate phase insoluble therein,commingling said extract phase with a liquid, normally gaseousanti-solvent, vaporizing a portion of said antisolvent, cooling saidextract phase by internal refrigeration and l separating from saidextract phase an intermediate raiilnate Vrendered insoluble in sai'dextract phase by said anti-solvent said intermediate raiilnatecontaining the bulk of said anti-solvent.

5. A process for the separation of parafilnic and vnon-paraiiinicfractions from mineral oil containing the same which comprisesextracting said oil with a selective solvent, separating the extractphase soluble in said solvent from the raillnate phase insolubletherein, heating a portion of said extract phase to 4vaporize solvent,removing said vapors frcm said heated portion, intermixing the unheatedportion of said extract phase with the heated portion, commingling saidextract phase with an anti-solvent and separating from said extractphase an intermediate raffinate rendered insoluble in said extract phaseby said anti-solvent said intermediate ramnate containing the bulk ofsaid anti-solvent.

marc B'. BRAY

